Method for inspecting coated surfaces



July 21, 1942. I F. DIEFFENBACH 7 2,290,170

METHOD FOR INSPECTING COATED SURFACES Filed Oct. 8, 1940 Patented July21, 1942 METHOD FOR INSPECTING COATED SURFACES Ferd Dieflenbach,Pittsburgh, Pa. Application October'8, 1940, Serial No. 360,246

(Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 0. G. 757) 3 Claims.

This invention described herein may be manu factured and used by or forthe Government for governmental purposes, without the payment to me ofany royalty thereon.

This invention relates generally to a method for the inspection ofprotective coatings, but more particularly to the microscopic inspectionof cross-sectional areas of coated surfaces.

One object of the invention is to provide a simple and effective methodfor preparing coated surfaces for the microscopic inspection of theadhesive union between the layers of said coatings and the surface overwhich they are spread.

Another object of the invention is to provide a simple, efiicient andeconomical method for preparing coated surfaces and exposingcrosssectional areas thereof for microscopic inspection.

Another object of the invention is to provide a method for the study ofpaint and painted surfaces in a manner similar to metallography in whichthe structures of metals are microscopically inspected and studied Withthese and other objects in view this invention consists in certain noveldetails of construction, combination and arrangement of parts, to bemore particularly hereinafter set forth and claimed.

Referring to the figures in which like parts are represented by similarreference characters:-

Fig. 1 is a perspective view illustrating separated uncoated inspectionblocks;

Fig. 2 is a perspective view showing the inspection blocks united andcoated on one surface;

.Fig. 3 is a perspective view illustrating the I blocks separated as inFig. l, but with coated surfaces;

Fig. 4 is a side elevation showing an inspection block mounted upon thestage of a microscope; and

Fig. 5 illustrates an enlarged cross-section of the coatings as viewedthrough the eyepiece of the microscope.

Referring to Fig. 1 it will be noted that the apparatus comprises twoinspection blocks Ill and I0 which are provided with smooth lateralsurfaces, and are drilled respectively at II and II and I2 and I2 forthe reception of bolts I3 and i3, which are adapted to detachablyconnect the blocks and hold them tightly united by means of the nuts l4and I4 as shown in Fig. 2.

These testing blocks may be made of steel, aluminum, wood, plastic orany other suitable material depending on the type and quality of 55 byexamination without reagents. Such examithe protective coating which isto be inspected or the material which it is desired to coat. so as toascertain the adhesive qualities of the coating with respect to saidmaterial.

After connecting the blocks l0 and Ill and fastening them tightlytogether by screwing up on the nuts l4 and I 4, one of the lateralsurfaces extending over both of the blocks I0 and I0, is given one ormore coats of paint, varnish, enamel or other protective coating whichit is desired to inspect, as indicated by the numeral l5, Fig. 2.

After the coating or coatings l5 have completely dried the nuts I4 and Mare unscrewed from the bolts l3 and I3 and the blocks Ill and I0separated as shown in Fig. 3, thus splitting the coated surface along acentral edge, as indicated by the numerals l6 and I6.

One of these blocks Ill or ID is then placed on the stage l'l (Fig. 4)of a microscope l8 with the split edge It ofthe coated surface I5directly beneath the objective lens (not shown), and the microscopeadjusted and focused in the usual manner for microscopic inspection ofthe crosssuch as the following:

(a) Adhesion between successive coats of paint in a paint system seemsto be partially dependent upon the interlock of pigment particles. Thisexplains, at least partially, the very decided lack of adhesion betweendissimilar coatings ina paint system,

(b) The structure of certain paint films are heterogeneous throughouttheir thicknesses, the study of which is very important in that a paintfilm, particularly under water, must be stable throughout its thickness.

(0) The reason for the blistering of paints containing certain amountsof zinc yellow has been discovered.

The technique involved in the use of this device may be diversified inmany ways. The

cross-sections are studied similarly to metal-v lography specimens, thatis, by treating with various reagents to etch or react with variousconstituents of the paints to be studied. However, much can bedetermined with this device face of two adjoining detachably connectedinspection blocks, allowing the coating to dry and then separating saidblocks to fracture the coating along the line oi jointure of said blocksto expose cross-sectional areas of the divided coating.

a A method for determining the adhesive thereof comprising, coating acommon plane sur- I qualities of coated surfaces comprising, coating acommon plane surface of two adioining detachably connected inspectionblocks, allowin the coating to dry, separating said blocks to fracturethe coating along the line of jointure of said blocks and placing across-sectional area of the divided coating in the field of a microscopefor inspection of the internal structure of the coating along theruptured edge.

3. A. method. for preparing coated surfaces for 'microscopic inspectioncomprising, coating a continuous surface of two adjoining detachablyconnected inspection blocks, allowing the coating to dry' and thenseparating said blocks to fracture the coating along the lineof jointureof said blocks to expose cross-sectional areas of the divided'coating.

FERD DIEFFENBACH.

